1. Field of the Invention
The present invention relates to a hand-held power tool such as, e.g., a chisel or combination hammer and including a motor-driven pneumatic percussion mechanism that includes a guide tube, an impact member displaceable in the guide tube, a reciprocating driving member for driving the impact member, a gas spring located between the driving member and the impact member for transmitting a driving motion of the driving member to the impact member, a motor-driven eccentric wheel rotatable about a stationary, with respect to the power tool, axis and a connection rod eccentrically supported on the eccentric wheel and connected to the driving member for converting a rotational movement of the eccentric wheel into a reciprocating movement of the driving member
2. Description of the Prior Art
European Publication EP 1 584 422 A1 discloses an electrically driven drilling and/or chisel hammer having a percussion mechanism located in the tool housing and driven by a motor. The percussion mechanism includes a driving member such as a driving piston displaceable in a guide tube and movable to and from by a motor-driven connection rod. The connection rod is eccentrically supported with its end remote from the driving piston on an eccentric wheel rotatable about a stationary axis. The driving member drives, via an air cushion or an air spring, a percussion piston likewise displaceable in the guide tube. The percussion piston imparts blow via an anvil to a working tool receivable in the chuck of the power tool. In order to reduce peak pressures in the percussion mechanism, there is provided, between the driving piston and the percussion piston, in addition to the air or gas spring, an elastic mechanical compression spring. Such a percussion mechanism is very robust and powerful.
An object of the present invention is to optimize the pressure surge in the percussion mechanism in a constructively simple manner.